1. Field of the Invention
The present invention relates to an apparatus or device which indicates torque load in an operating propeller shaft driven machine. More particularly, the present invention relates to a device employed to accurately measure the increased torque load along the drill string of an oil well drilling rig.
2. Prior Art
Most oil well and water well drilling machines or rigs are provided with a rotary table. The rotary table is attached to a section of pipe called a "Kelley", which in turn is connected to the drill string in the well bore. The rotary table rotates the Kelley thus rotating the boring bit. There are two methods of turning the rotary table, the first method being a chain driven rotary table and the second method being a rotating shaft connected directly to the rotary table through suitable gearing, etc. The rotating shaft drive is commonly referred to herein as a propeller shaft drive.
Hazards can occur during the drilling process such as the drill bit encountering a stratum of hard rock or having the sides of the well hole collapse inwardly on the drill string. These various hazards can impede the rotation of the drill string thus locking it from turning. If continued power is applied to the rotary table, a twisting off of the Kelley from the drill string can occur, which requires a costly reinstitution of the drilling operation. Therefore, the purpose of a torque indicator is to prevent a costly "twist-off" and to provide a continuous visual and permanent record of the delivered torque load in the propeller shaft drive.
Torque indicators used on certain oil well drilling rigs are well known in the prior art. The prior art torque indicators for rotary drilling are applied to a chain driven rotary table wherein a movable idler is placed on the power side of the chain drive in a position to deflect the straight line of the drive between drive and driven sprockets. As the torque increases and tightens the chain, the deflection of the imposed idler is proportional to the torque load and is recorded as such on an indicator. However, the aforementioned torque indicator is not applicable to a propeller shaft driven rotary table.
One prior art patent, U.S. Pat. No. 4,193,720 to Machida, discloses a critical torque indicator having input and output members which are connected so as to rotate conjointly whenever the torsional resistance is lower than a set critical value. Upon the occurrence of a greater torque, the output member will delay in rotation as compared to the input member, wherein the difference in their rotational speed is taken out as a signal to detect critical torque. However, the Machida patent was designed for us with a machine tool drill and is not applicable for use with a propeller shaft driven rotary table.
No prior art device incorporates splined ends on its input and output members. No prior art discloses the use of a chamber which is provided with an internal compression spring to impede longitudinal movement of the input member during normal operation. No prior art uses longitudinal movement of the input member as the measure of critical torque load.